Indicator tube having means for separating leads

ABSTRACT

A miniature, cold cathode, gas-filled indicator tube which has an envelope of minimal diameter and length and includes an anode electrode and a stack of cathode character electrodes. The cathode electrodes include closely spaced cathode tabs to which similarly closely spaced tube pins are secured. The tube pins extend from the cathode tabs through the stem of the envelope so that they are accessible outside the tube. The tube pins are bent and spread apart as they pass through the stem so that they are relatively widely spaced outside the envelope adjacent to the tube stem.

States Pate [72] Inventor Thomas D. Peterson Somerville, NJ. [21] Appl. No. 797,915 [22] Filed Feb. 10, 1969 [45] Patented Nov. 9, 1971 [73] Assignee Burroughs Corporation Detroit, Mich.

[54] INDICATOR TUBE HAVING MEANS FOR SEPARATING LEADS 3 Claims, 7 Drawing Figs.

[52] US. Cl SIS/109.5, 313/290, 313/318, 315/84.6 [51] Int. Cl ..l-I01j 61/36, HOlj 11/66 [50] Field ofSearch 313/1095, 318, 49, 51, 285, 290; 315/84.6

[56] References Cited UNITED STATES PATENTS 1,960,245 5/1934 Henninger, Jr 313/109.5

2,991,338 7/1961 Wightman 3,437,861 4/1969 Koshizukaetal Primary Examiner-Roy Lake Assistant Examiner-E. R. LaRoche Attorneys-Kenneth L. Miller, Robert A. Green and Charles S. Hall ABSTRACT: A miniature, cold cathode, gas-filled indicator tube which has an envelope of minimal diameter and length and includes an anode electrode and a stack of cathode character electrodes. The cathode electrodes include closely spaced cathode tabs to which similarly closely spaced tube pins are secured. The tube pins extend from the cathode tabs through the stem of the envelope so that they are accessible outside the tube. The tube pins are bent and spread apart as they pass through the stem so that they are relatively widely spaced outside the envelope adjacent to the tube stem.

PATENTEDunv 9 IQ'II 3,519,693

sum 1 [1F 2 IN VliN'IOR.

THOMAS D. PETERSON AT TORNE Y PATENTED 9 3,619,693

SHEET 2 OF 2 250 290 INVEN'IOR. THOMAS D. PETERSON FIGJ 8m ATTORNEY INDICATOR TUBE HAVING MEANS FOR SEPARATING LEADS BACKGROUND OF THE INVENTION Indicator tubes of the general type described above have been manufactured successfully and have been used commercially for many years. However, the ever-present need to miniaturize and to reduce the cost of manufacture of these tubes has presented problems which are not solved in the prior art One problem area involves the stern of the tube and the relationship between the cathodes and the tube pins which are secured to the cathodes and extend through the tube stem.

One tube construction having an envelope of about 55-inch diameter includes a stack of ten cathodes having tabs at their lower ends welded to tube pins which extend from the cathodes vertically downward through the stem of the tube. In the most convenient arrangement, the cathode tabs at the lower ends of the cathodes are aligned in two closely spaced rows, and the tube pins or leads extend directly down from the tabs through the stern in two similar closely spaced rows. Of course, the leads are also arranged in the same two closely spaced rows outside the tube adjacent to the stem. In miniature tubes, the pins or leads are fine, flexible wires, and, since they are so closely spaced, they are difficult to handle, and they become entangled quite readily. Thus, it is difficult to mount a tube in a socket or on a printed circuit board or the like.

In one arrangement to facilitate handling such tubes, an auxiliary insulating socketlike member is coupled to the leads to spread them apart and insulate them from each other so that the tube can then be mounted on a printed circuit board or the like. This represents an undesirable added expense, both for the part and for the labor and time required to secure it to a tube.

SUMMARY OF THE INVENTION Briefly, a display tube embodying the invention includes an anode electrode and a compact stack of cathode electrodes having leads secured to tube pins in the base of the tube. The tube pins inside the tube are very close together; however, the stem and the pins are so constructed that the piris are more widely spaced apart outside the tube where they are connected to operating circuitry.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view of a multiple cathode indicator tube embodying the invention;

FIG. 2 is a sectional view of a portion of the base or stem of the tube of FIG. 1 and some of the associated electrodes;

FIG. 3 is a sectional view similar to the view of FIG. 2 showing a modification of a portion of the tube of FIG. 1;

FIG. 4 is a plan view of a portion of the tube elements shown in FIG. 2;

FIG. 5 is a plan view showing one arrangement for securing the upper ends of the cathode electrodes of the tube of FIG. 1;

FIG. 6 is a perspective view of a tray which may be used to secure the upper cathode tabs of the cathode electrodes; and

FIG. 7 is a side view of the elements of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT An indicator tube 10 embodying the invention and shown in FIG. 1 includes an envelope 21 which is filled with an ionizable gas such as neon, argon, or the like and mercury, if desired, at a suitable pressure. The envelope includes a front wall 22 which comprises a viewing window, through which glowing cathode character electrodes 23 may be viewed. The envelope 21 includes a base or stem 24, through which metal pins or leads 25, 26 and 28 extend. The tube pins 25 are secured to cathode tabs 29 at the lower ends of the cathode electrodes, and pins 26 and 28 are secured to an anode electrodc, to be described. Tube 10 is a miniature tube, and pins or loads 25, 26, and 28 are thin, flexible wires.

Ten cathodes 23 in the form of numerals 0 to 9 are normally employed in tube 10, and it can be seen that, when 10 cathodes are placed in a tube of perhaps lfi-inch diameter, the cathode tabs 29 and the tube pins 25 are positioned quite close together. In order to maintain the close spacing between the cathodes themselves while increasing the effective spacing between the cathode tabs and tube pins, the cathode tabs on adjacent cathodes are offset from each other (FIGS. 2 and 3) so that the tabs and their pins are arrayed in two parallel rows along and close to a diameter in the stem. This arrangement, among other things, facilitates the welding of each tube pin to its cathode. However, the pins 25 could be aligned in a single row, if desired. Two rows of pins are shown and described.

The upper end 60 of the envelope 21, remote from the stem 24 is known as the dome of the envelope and is flat and carries a tubulation 61 for evacuating the envelope and filling it with the desired gas atmosphere which may be argon, neon, or the like. The flat dome and flat base minimize the overall length of the envelope. However, a flat dome is not essential to practice the invention.

The stem 24 is a generally flat disk except for a central raised portion 81 which extends from front to rear of the tube along the central diameter of the stem which is perpendicular to the center of the viewing window 22. The stem and its raised portion 81 may comprise a unitary glass or ceramic piece, or it might be made up of two pieces, held together in any suitable fashion. The raised portion 81 includes a flat upper surface 90, and its sidewalls 91 may be flat or curved. Ten tube pins 25 for connection to the ten cathodes 23 normally used in tube 10 and anode pin 28 are embedded in the raised portion 81 and extend a short distance above the flat upper surface 90. Each pin 25 and 28 has a glass boss I00 surrounding it where it emerges from the surface (FIGS. 2 and 3) of the raised portion 81.

According to the invention, the pins 25 (and 28, if necessary) are bent, and they are also positioned at angles with respect to each other as they extend from the cathode tabs through the tube stem and out of the tube stem to provide maximum spacing between them outside the tube adjacent to the lower surface of the stem. The bent portion of each pin is positioned within the stem. Considering a sectional view through the stem (FIGS. 2 and 3), each of the pins has a first portion 32 which extends vertically downwardly from its cathode tab 29 and partly into the stem, a bent portion 34 which extends or bends outwardly from the axis through the first portion and lies within the stem, and a third vertical portion 36 which is parallel to the first portion but is more remote therefrom and closer to the periphery of the stem. The third portion originates within the stem and extends out of the stem and is accessible outside of the tube. In addition, referring to FIG. 4 and looking down on the stem, each of the pins is oriented by being pivoted about its first portion as an axis so that adjacent third portions 36 and the portions thereof outside the tube are at a maximum spacing from each other.

In a preferred arrangement of the pins 25, the bent portions are of such length and are bent at such an angle with respect to the first portions that the third portions 36 are oriented in two rows of aligned pairs of pins. Thus, the external portions of the pins are not staggered, but, in each pair, the pins are side by side. The net effect then is to convert two staggered rows of pins at one spacing inside the tube, to two aligned rows of sideby-side pins at a greater spacing outside the tube where they can be handled with relative ease.

If space requires, pin 28 may also be bent. Since pins 26 can be used to provide anode potential, pin 28 might be omitted, if necessary.

The raised portion 81 of stem 24 is not required under all circumstances; however, it serves the useful purpose of elevating the cathode character electrodes 23 above the base of the tube. The elevation of the cathodes improves the angle of viewability when, in operation, a tube is positioned above the viewer, and it also pennits auxiliary electrodes, such as decimal points, commas, or the like (to be described), to be positioned near the cathode electrodes, but with minimum interaction between them and the cathode characters.

It has been found desirable, but not necessary, to provide a metallic shield 110 on the stem 24 in operative relation with the pins 25 and their connections to the cathode electrodes 23 to prevent the formation of continuous paths of sputtered metal. The shield 110 may be a separate plate, or it may be a metal film formed in any suitable manner.

In one embodiment shown in FIGS. 2 and 4, the plate 110 is generally T-shaped and includes a main body portion 120, which extends along the length of the raised portion 81 of the stern, and a transverse arm 132 at the rear of the tube. The plate 110 includes three star-shaped apertures 148 positioned at its corners which receive tube pins 26 and 28 which make electrical contact therewith by means of a mechanical tight fit. Pins 26 and 28 are connected to the tube anode to be described. The main body 120 of the plate 110 includes a plurality of apertures 150 which are arranged in two rows to receive pins 25. The apertures 150 are of greater diameter than pins 25 so that the plate and pins are insulated from each other. Plate 110 actually seats on the glass bosses 100 around the pins 25, and the bosses project slightly into the apertures 150.

In a modification of the shield 110, referring to FIG. 3, two side panels 151 are provided extending from the main body 120 near the front of the tube. The side panels 151 preferably bend downwardly and follow the contour of the sidewalls of the raised portion 81 of the stern and the top surface 156 of the stem. The side panels extend laterally sufliciently so that they lie between, or shield, the auxiliary characters 158 (to be described) from the surface 156 of the stern (FIG. 3).

The electrode assembly of tube 10 normally includes a stack of l cathode electrodes 23 which are in the form of numerals 0 to 9 and a tubular anode electrode which surrounds and encloses the cathode electrodes. The anode electrode includes a solid backplate 170 and a front mesh screen 180 which curve and meet each other at the sides of the cathode stack where they merely touch or are welded together. The two pins 26 are welded to the anode backplate 170, and the leading pin 28 is welded to the front screen to provide support and electrical contact.

Each cathode electrode 23 is of metal and includes a main body portion in the shape of a character and upper and lower tabs 30 and 29, respectively, which are used for mounting and supporting the cathode. The lower mounting tab 29 of each cathode is welded to a tube pin 25. Each tab 29 is approximately as long and wide as the portion of its pin 25 which rises above its boss 100, and the lower edge 210 of the main body portion of the cathode meets the upper end of its pin 25. With two rows of pins 25, adjacent cathodes are connected by their tabs 29, one to a pin in one row and the next to a pin in the other row, etc. Thus, the lower tabs 29 are properly positioned on the main body portion of the cathodes during manufacture so that, when arranged in a stack, each tab 29 is aligned with its proper pin 25, as can be seen in FIGS. 2 and 3. The upper tabs 30 may or may not also be arranged in two rows.

The upper ends of the cathodes may be unsupported, if desired, or they may be supported in different ways. In one arrangement (FIG. a post 220 is supported by welding or by means of eyelets between the front anode screen 180 and the rear plate 170. The post is either of insulating material, or it is coated with insulating material, and the cathodes 23 are held in place thereon by means of their upper tabs 30) which are apertured and through which the post 220 extends. Insulating washers 230 are mounted on the post between adjacent cathode tabs in this arrangement.

In another arrangement (FIGS. 1, 6, and 7), a tray 240 of a ceramic material is secured between the front screen and rear plate, for example by means of tabs 242 or the like, which pass through slots in the tray. The bottom wall 250 of the tray is provided with slots 260 through which the cathode tabs 30 extend into the tray. An insulating cement, such as a mixture of chrome oxide and sodium silicate, is placed in the tray and embedding tabs 30 to secure the cathode tabs and their cathodes in place. The cement forms a unitary mass 252 enclosing the cathode tabs.

The tube 10 also includes the auxiliary characters 158 which are located on both sides of, and below, the stack of cathode characters generally at positions which such characters would normally occupy. Each auxiliary character includes a pin 300 carried by stem 24, a ceramic washer 310 threaded on pin 300 and seated either on the stem or on arm 151 of plate 110. A metal disk 320 of cathode material and operable to represent a decimal point is positioned with its lower edge resting on the washer 310, and it is welded to pin 300. Of course, electrode 320 could be shaped as a comma or some other character.

It is noted that the elevation of the cathode characters 23, due to the raised portion 81 of the stem 24, permits the auxiliary character electrodes 320 to be positioned below them sufficiently so that there is no interaction or interference during tube operation.

It is also desirable to provide a metal shield plate or film 290 on the lower surface of the tray 240 used to support the upper cathode tabs 30. This plate 290 is apertured to permit the tabs 30 to pass through without making contact with it, and the plate is electrically connected by a tab, e.g., tab 242, or the like to the rear anode plate or to the anode screen.

It can be seen from the foregoing description that the present invention provides a multicathode indicator tube which is favorably compact and miniaturized. In addition, the tube leads, which are fine and flexible, are sufficiently widely spaced that they can be handled with ease.

What is claimed is:

I. In a miniature cathode glow indicator tube including an envelope, at least one anode located in said envelope, a stack of cathodes centered substantially along a diameter of said envelope, a plurality of fine, flexible wire leads connectable to said cathodes and anode for connecting said cathodes and anode to points outside said envelope, the improvement comprising:

a stem assembly means sealable to said envelope to close it off, for locating substantially half the internal ends of said wire leads on each side of said diameter to form two rows of lead ends within said envelope, and for spacing apart the outwardly extending portions of said wire leads to form, external to said envelope, wider spaced and lengthened rows of lead ends with respect to the rows of lead ends within said envelope, said wire leads passing through and sealed within said stem assembly.

2. The cathode glow indicator tube improvement of claim I wherein said stern assembly means includes an elevated portion extending along said diameter, said two rows of lead ends within said envelope protruding from said elevated portion.

3. The cathode glow indicator tube improvement of claim 1 further including a metallic shield having apertures therethrough for passage of said internal lead ends, said shield disposed along said diameter on the side of said stem assembly means internal to said envelope.

* t i i t 

1. In a miniature cathode glow indicator tube including an envelope, at least one anode located in said envelope, a stack of cathodes centered substantially along a diameter of said envelope, a plurality of fine, flexible wire leads connectable to said cathodes and anode for connecting said cathodes and anode to points outside said envelope, the improvement comprising: a stem assembly means sealable to said envelope to close it off, for locating substantially half the internal ends of said wire leads on each side of said diameter to form two rows of lead ends within said envelope, and for spacing apart the outwardly extending portions of said wire leads to form, external to said envelope, wider spaced and lengthened rows of lead ends with respect to the rows of lead ends within said envelope, said wire leads passing through and sealed within said stem assembly.
 2. The cathode glow indicator tube improvement of claim 1 wherein said stem assembly means includes an elevated portion extending along said diameter, said two rows of lead ends within said envelope protruding from said elevated portion.
 3. The cathode glow indicator tube improvement of claim 1 further including a metallic shield having apertures therethrough for passage of said internal lead ends, said shield disposed along said diameter on the side of said stem assembly means internal to said envelope. 